1. Field of the Invention
The present invention relates to a synthesis method and, more particularly, to a synthesis method for preparing TFPX (tetrafluoro-p-xylene).
2. Description of Related Art
Because parylene polymer possess numerous advantages for manufacturing purposes, for example, maintaining the coating environment at room temperature, no residual stress resulting after coating and allowing precise controls on the thickness of the depository film along with parylene polymer's uniformity, excellent acid and alkali resistance and low dielectric properties, parylene polymer has been widely employed in the practice of electric insulation on printing electric circuit boards, damp-proofing on sensors or medical equipment, preventing corrosion on metal coating, etc. Presently the highly anticipated fluoro parylene polymer, noted for its low dielectric constant and high melting point, will be utilized in dielectric coating in the electrical and coating industries.
Fluoro parylene polymer has the structure (1) as follows:

Fluoro parylene polymer generally is coated on products by means of chemical vapor deposition in a vacuum state at room temperature. Products coated with parylene polymer possess not only excellent anticorrosive, damp-proof and insulating characteristics, but also have the advantages of being extra-thin, transparent and poreless. Parylene polymer coating is to polymerize the more active monomer on the surface of the object. Unlike the general steps of liquid coating process, this coating process has the polymer (dimer) vaporized first, and the dimer (para-xylylene) bonds are cleaved to yield monomer radical at pyrolysis condition, whereafter it is finally polymerized to form parylene polymer.
Moreover, fluoro parylene polymer's dielectric constant decreases as the quantity of fluorine atoms increases within the polymer, thus octafluoro-2,2-paracyclophane, which is generally used nowadays, has the following structure (2):

TFPX (α, α, α′, α′-tetrafluoro-p-xylene), as the molecular structure below shows, is a critical starting material in the process of synthesis for the above dimer.

However, the TFPX synthesis method nowadays is relatively costly, time-consuming and unable to be mass-produced. For example, although TFPX can be obtained from the preparation by mixing TCPX (α, α, α′, α′-tetrachloro-p-xylene) with KF at proper ratio in either an open or closed reaction container, reacting continuously for 12 hours at a temperature of 260° C.˜280° C., a lack of solutions in the reaction will cause a serious gelation problem, similar to what would happen in a solid-state reaction. Such a problem not only hinders the yield of the desired product, it yet further affects the possibility of production expansion. Other typical synthesis methods involve organic compounds comprising carbonyl group, such as terephthaldehyde, to be fluorinated with fluorinating reagents, for example SF4, MoF6, DAST or HF/Py at proper conditions. Although a better yield of TFPX can be achieved from such preparation, the price of the above-mentioned fluorinating reagents can be rather high. The equipments and preparation conditions can also be relatively unique and complicated, and the leftover gases and liquid wastes are difficult to deal with, thereby greatly raising the cost of preparing TFPX and thus making these methods unfavorable with respect to mass production.
Therefore, it is desirable to provide a safe, cost-effective and efficient synthesis method, such that a reduction in the cost of preparing TFPX can play a positive role in production expansion.